Systems and methods for compensating long term sensitivity drift of electrochemical gas sensors exposed to nitric oxide
Inventors
Tolmie, Craig R. • Milsap, Jeff • Acker, Jaron M.
Assignees
Mallinckrodt Pharma IP Trading DAC • Mallinckrodt Pharmaceuticals Ireland Ltd • Therakos Inc • INO Therapeutics LLC • Mallinckrodt Critical Care Finance Inc
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Publication Number
US-11141549-B2
Publication Date
2021-10-12
Expiration Date
Abstract
Described are systems and methods for compensating long term sensitivity drift of catalytic type electrochemical gas sensors used in systems for delivering therapeutic nitric oxide (NO) gas to a patient by compensating for drift that may be specific to the sensors atypical use in systems for delivering therapeutic nitric oxide gas to a patient. In at least some instances, the long term sensitivity drift of catalytic type electrochemical gas sensors can be addressed using calibration schedules, which can factor in the absolute change in set dose of NO being delivered to the patient that can drive one or more baseline calibrations. The calibration schedules can be used reduce the amount of times the sensor goes offline. Systems and methods described may factor in in actions occurring at the delivery system and/or aspects of the surrounding environment, prior to performing a baseline calibration, and may postpone the calibration and/or rejected using the sensor's output for the calibration.
Core Innovation
The invention relates to a gas delivery system for delivering therapeutic gas comprising nitric oxide from a therapeutic gas source to a breathing circuit of a patient, and for measuring a concentration of the therapeutic gas using at least one sensor. The system controller includes a processor in communication with memory that stores a calibration schedule and a calibration line correlating expected sensor output values to therapeutic gas concentration.
A central aspect is that the system controller adjusts the measurements of the sensor according to the correlation of sensor outputs to therapeutic gas concentration, and causes calibration according to the calibration schedule that dictates when baseline calibrations should occur. The calibration schedule is changed upon a change in a set dosage, and is based on the set dosage.
During the plurality of baseline calibrations, the sensor measures an actual output value indicative of a zero concentration of the therapeutic gas while only being exposed to a gas having a zero concentration of the therapeutic gas. The system controller then adjusts the correlation of expected sensor output values to therapeutic gas concentration according to the difference in the actual output value and the expected output value, including offsetting the calibration line by the absolute value of the output value indicative of a zero concentration of the therapeutic gas.
The disclosed approach compensates long-term sensitivity drift of catalytic type electrochemical NO gas sensors by using baseline/span calibration tied to absolute changes in set NO dose and by updating calibration lines via baseline zero offsets and slope changes. The system further accounts for measurement timing relative to alarm status by postponing or rejecting baseline calibration actions based on an alarm condition, user interaction, and interfering gas or out-of-threshold sensor outputs.
Claims Coverage
The independent claims cover a nitric-oxide therapeutic gas delivery system that uses a stored calibration schedule and a calibration line to adjust sensor measurement correlations, including baseline calibrations that use zero-concentration exposure and offset calibration lines based on a measured zero output. Across the independent claims, the inventive features include scheduling and changing baseline calibration timing based on set dosage; performing zero-indicative baseline calibration under zero-concentration exposure; adjusting measurement correlations by difference or offset of zero-indicative output; and postponing calibration in response to alarm conditions.
Therapeutic nitric-oxide gas delivery with sensor calibration correlation
A gas delivery system having a gas delivery subsystem configured to deliver therapeutic gas comprising nitric oxide from a therapeutic gas source to a breathing circuit of a patient, with a calibration schedule and a calibration line correlating expected sensor output values from at least one sensor to therapeutic gas concentration, wherein the system controller adjusts the measurements of the at least one sensor according to the correlation of sensor outputs to therapeutic gas concentration.
Baseline calibration schedule tied to set dosage changes
The system controller causes the at least one sensor to be calibrated according to the calibration schedule that dictates when the plurality of baseline calibrations should occur, wherein the calibration schedule is changed upon a change in a set dosage, wherein the calibration schedule is based on the set dosage.
Zero-concentration exposure baseline calibration and correlation adjustment
During the plurality of baseline calibrations the at least one sensor measures an actual output value indicative of a zero concentration of the therapeutic gas while only being exposed to a gas having a zero concentration of the therapeutic gas, and wherein the system controller is configured to adjust the correlation of expected sensor output values to therapeutic gas concentration according to the difference in the actual output value and the expected output value.
Breathing circuit and continuous nitric-oxide sensor with calibration line offset
A gas delivery system with a breathing circuit configured to deliver nitric oxide to a patient and a nitric oxide sensor configured to continuously measure a concentration of nitric oxide in the breathing circuit and communicate with the system controller, wherein the system controller adjusts the measurements according to the calibration line and offsets the calibration line by the absolute value of the output value indicative of a zero concentration of nitric oxide.
Calibration schedule scheduling and change based on input set dosage
The system controller identifies according to the calibration schedule in the memory when the plurality of baseline calibrations is intended to be performed, accounting for the input set dosage, and schedules a time for executing the plurality of baseline calibrations according to the calibration schedule, wherein the system controller changes the calibration schedule upon a change in the input set dosage, wherein the calibration schedule is based on the input set dosage.
Four-terminal electrochemical nitric-oxide sensor calibration with zero offset
A gas delivery system using at least one four terminal electrochemical nitric oxide gas sensor configured to continuously measure a concentration of nitric oxide in the breathing circuit and communicate with the system controller, wherein the calibration line correlates expected sensor output values from the at least one four terminal electrochemical nitric oxide gas sensor to nitric oxide gas concentration and the system controller offsets the calibration line by the absolute value of the output value indicative of a zero concentration of nitric oxide.
Baseline calibration timing varies sooner with larger set-dosage change
The system controller is configured to identify according to the calibration schedule in the memory when the plurality of baseline calibrations is intended to be performed accounting for the input set dosage, wherein the plurality of the baseline calibration occurs sooner based upon a larger change in set dosage.
Postponing baseline calibration based on alarm condition timing
The system controller delays a scheduled calibration of at least one sensor when an alarm condition occurs within a predetermined time interval before the calibration, and where the claim further includes delaying calibration when an alarm is active or was active within a predetermined timeframe before the scheduled calibration time.
Overall, the independent claims require a controller-managed calibration schedule and calibration line for nitric-oxide sensor measurement correlation, with baseline calibrations using a zero-concentration exposure and controller adjustment or offset of calibration correlation based on a measured zero-indicative output. Additional independent coverage includes continuous nitric-oxide sensing in a breathing circuit, use of at least one four terminal electrochemical nitric oxide gas sensor, earlier calibration when set dosage changes more, and postponement of scheduled calibration based on alarm timing.
Stated Advantages
Compensating long-term sensitivity drift of catalytic type electrochemical NO gas sensors in therapeutic inhaled nitric-oxide delivery systems.
Updates calibration lines using baseline zero offsets and slope changes based on absolute changes in set NO dose.
Allows calibration timing to be postponed or rejected based on alarm status, user interaction, and interfering gas or out-of-threshold sensor outputs.
Documented Applications
Therapeutic inhaled nitric-oxide delivery systems using catalytic type electrochemical NO gas sensors, where long-term sensitivity drift is compensated.
Nitric oxide gas monitoring and calibration during operation of a breathing circuit/ventilator system with alarm handling and calibration scheduling.
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